Digital based electronic media formats are completely replacing the legacy analog electronic media formats. In the audio domain, digital compact discs (CDs) replaced analog vinyl recordings many years ago. Analog magnetic cassette tapes are becoming increasingly rare. Second and third generation digital audio systems such as Mini-discs and MP3 (MPEG Audio—layer 3) based formats are now taking away market share from the first generation digital audio format of compact discs.
Film-based still photography is rapidly being replaced by digital still photography. Immediate image availability and image distribution via the Internet have provided users with irresistible features.
However, the video domain has been slower to move to digital storage and transmission formats than audio and still images. This has been largely due to the massive amounts of digital information required to accurately represent video in digital form. The massive amounts of digital information needed to accurately represent video require very high-capacity digital storage systems and high-bandwidth transmission systems.
But the video domain is finally adopting digital storage and transmission formats. Faster computer processors, high-density storage systems, high-bandwidth optical transmission lines, and new efficient video encoding algorithms have finally made digital video systems practical at consumer price points. The DVD (Digital Versatile Disc), a digital video system, has been one of the fastest selling consumer electronic products ever. DVDs have been rapidly supplanting Video-Cassette Recorders (VCRs) as the pre-recorded video playback system of choice due their exceptional video quality, high quality 5.1 channel digital audio, convenience, and extra features. In the realm of video transmission systems, the antiquated analog NTSC (National Television Standards Committee) video transmission standard is finally being replaced with the digital ATSC (Advanced Television Standards Committee) video transmission system that uses digital compression and encoding technology.
Computer systems have been using various different digital video encoding formats for a number of years. Among the best digital video compression and encoding systems used by computer systems have been the digital video systems backed by the Motion Pictures Expert Group commonly known by the acronym MPEG. The three most well known and highly used digital video formats from MPEG are known simply as MPEG-1, MPEG-2, and MPEG-4. Video CDs and consumer-grade digital video editing systems use the early MPEG-1 format. Digital Versatile Discs (DVDs) and the Dish Network brand Direct Broadcast Satellite (DBS) television broadcast system use the MPEG-2 digital video compression and encoding system. The MPEG-4 encoding system is rapidly being adapted by the latest computer based digital video encoders and associated digital video players.
The MPEG-2 and MPEG-4 standards compress a series of video frames or video fields and then encode the compressed frames or fields into a digital bitstream. The rate of the digital bitstream must be carefully monitored in order not to overflow memory buffers, underflow memory buffers, or exceed the transmission channel capacity. Thus, a sophisticated rate control system must be implemented with the digital video encoder that provides the best possible image quality in the allotted channel capacity without overflowing or underflowing buffers.